Metallic Thread

To prevent metallic thread from fraying on the reel - tie a knot in the thread at the cutting point, then cut the thread before the knot, thereby keeping the thread on the reel from fraying.
To prevent the thread slipping/falling out, knot the metallic thread at the eye of the needle.
Choose a needle with a slightly bigger eye
Use a shorter length of thread than usual. This will reduce tangle/stretch and will be easier to manage.
To create subtle highlights to your design try blending a strand of metallic thread with one of stranded cotton.
If you mix your threads, try to position the metallic thread so it lies on the top and not hidden by the stranded cotton (try pulling the thread of stranded cotton through first).
When ironing your completed design use a LOW heat and place a clean cloth between your stitching and the iron to prevent the metallic thread from 'melting'